The objective is the investigation of cyclic azo dioxides and the corresponding bisnitroso forms, species of potential value as cancer chemotherapeutic agents. The cyclic azo dioxides--polar, chemically unreactive species--constitute a masked form of the nitroso species--less polar and of moderate-to-high reactivity towards biological substrates in several distinctive and potentially selective ways. Specific objectives include the synthesis of cyclic azo dioxides of varying ring size and study of the azo dioxide-bisnitroso equilibria. Primary emphasis is attached to bis(ortho-nitroso-benzyl) systems, capable of wide variation in substituents for provision of a range of properties (lipophilicity, steric, electronic effects) of consequence in the biological evaluation of these substances. Prinicipal interest is associated with azo dioxides in the following series: 1,2-diarylethanes, substituted dibenzyl ethers, and substituted dibenzylamines. Related objectives involve new approaches to bisnitroso species and the investigation of protective groups for the nitroso functionality. Various double bond reagents will be examined in this regard, including an investigation of the reversible (pH-dependent) reaction of the nitroso group with sulfinic acids to form N-hydroxysulfonamides and other approaches to this, and related species. The findings in this investigation will be used to select and prepare a series of azo dioxides for testing as cancer chemotherapeutic agents.